GMC T-Series 1999 Owner's Manual page 56

When using the exhaust brake, the proper gear range
selection is important. The exhaust brake will be most
effective if the gear range selected is the lowest possible
range that does not allow the engine rpm to go more
than 200 rpm above the rated (full load) rpm as
shown on the Engine Information Plate.
(Do not exceed 2900 rpm.)
The accelerator and clutch pedals must be released in
order for the exhaust brake to engage. Whenever the
EXHAUST BRAKE switch is on, the light in the switch
will be on even if the exhaust brake is not engaged (due
to the position of the accelerator or clutch pedal).
Do not use the exhaust brake when running the engine at
-
idle during warm up or other extended periods.
Prolonged use of the exhaust brake during idling will
cause the engine to overheat.
2-20
CAUTION:
Be careful when using the exhaust brake or you
could lock the wheels and lose control of the
vehicle. Operators not familiar with an exhaust
brake should not use this brake on slippery
surfaces before learning to use it on dry surfaces.
If the vehicle's wheels begin to lock when using
the exhaust brake on slippery surfaces, switch the
exhaust brake off immediately. The exhaust
brake will turn off if the anti
is activated.
yellowblue
-
lock brake system